Advanced Materials Research Vols. 299-300

Abstract: The compositions of a series of ethylene-propylene copolymers were quantitatively determined by ¹³C-NMR at 300K in the solvent o-dichlorobenzene. The monomer composition and sequence distribution were analyzed. The glass transition temperature Tg, half temperature of decomposition and crystallinity were found to be closely related to the sequence structures of methylene. The Tg, half temperature of composition, and crystallinity appeared an abrupt change when the methylene length arrived 7~8 because of the movement of the ethylene segments. Also, the Tg of copolymers were simulated according to the monomer compositions. The simulated Tg tended to decrease with the increasing methylene, which was opposite to that of experimented. That was due to the increased crystallization along with the growth of methylene length. While the polymer was amorphous constructed in the simulation, the Tg tended to decrease with the increasing soft segment methylene.

Abstract: The thermal expansion and the Curie temperature of Gd₂Fe_16.5Cr_0.5 compound have been investigated by means of x-ray diffraction and magnetization measurements. The result shows that the Gd₂Fe_16.5Cr_0.5 compound annealed at 1243°C has a hexagonal Th₂Ni₁₇-type structure. Cr atom substituting for Fe atom can increase the Curie temperature obviously. In magnetic state, an anisotropic anomolous thermal expansion was observed. Along the c-axis, the average linear thermal expansion coefficient α_c=-2.79×10^-6/K in the temperature range 294-472K, and α_c =-3.09×10^-5/K in 472-592K. Along the a-axis, the average linear thermal expansion coefficient α_a =9.22×10^-6/K in 294-552K, and α_a =-1.41×10^-5/K in 552-592K. In the temperature range 472-592K, the average volume thermal expansion coefficient α_v =-2.14×10^-5/K. The mechanism of the thermal expansion anomaly of Gd₂Fe_16.5Cr_0.5 compound was discussed in this paper.

Abstract: The three-dimensional finite element model of cabin glass with surface scratch is built using the finite element software ANSYS, which is aimed to analyze the detailed stress around the scratch route tip. Then the fatigue notch factor can be gained through utilizing of results from three-dimensional model, which is followed by the estimation of fatigue life based on local stress-strain method. It is found that the stress around scratch route tip is nearly linearly increased with the increasing of tip depth (0.2mm<h<0.8mm) and the fatigue performances of cabin glass with surface scratch are sensitive to scratch depth. Finally, fatigue tests are carried out with the specimens of different scratch route tip depths, and validation against fatigue life by local stress-strain method and experimental data shows a good agreement, which indicates that the scratch model and the local stress-strain method for the effects of scratch on cabin glass fatigue performances are valid.

Abstract: The low alloyed bainite ductile iron is obtained by alloying and austempering in room-temperature machine oil. The microstructure is investigated. The mechanical properties are discussed. In general, the number of white-bright zones and segregation is increasing with the increasing in the content of Mn, but the impact toughness is decreased. Therefore, the content of Mn is no more than 0.5 wt.%. The microstructure of bainite, martensite and a little retained austenite in the matrix of the ductile iron was investigated by scanning electron microscope (SEM). The hardness and impact toughness of the ductile iron subjected to heat-treatment are 54~56 HRC and 14.2 J/cm², respectively. The substitution of 0.3~0.5wt.% Mo by 0.7~1.0 wt.% Mn can be realized in the bainite ductile iron.

Abstract: A modified high Cr ferritic heat-resistant steel was developed and subjected to the thermomechanical treatment. The effect of applied stress and temperature on martensitic transformation and microstructure was studied by using high-resolution differential dilatometer and optical microscope. Applied stress raises the amount of defection as dislocation and grain boundary defects, thus elevate M_s. Applied stress also lead to the increase of transformation time due to the mechanical stabilization of austenite. Increase of applied stress or temperature would enhance these above effects.

Abstract: A strong pulse electromagnetic field was employed to treat the surface layer of several metal materials. The results showed that the treatment of the strong pulse electromagnetic field could modify the microstructure of the region around the crack on the 45^# steel surface. It could also make the recovery process occur in the scratch on the brass surface, and make the surface layer of the Wood’s alloy melt in a very shot time. These results indicated that the strong electromagnetic pulse could be developed as an effective non-contact method for the metal surface processing.

Abstract: A new phase field model coupled with external field was used to simulate 2D and 3D grain growth processing. The simulation results showed that 2D grain size distribution under external field was inhomogeneous. The evolutions of 2D grain under different external field strength were roughly the same, but the grain number was obviously different with the changes of external fields. Under the external field, the relationship between 2D grain area and time was linear. 3D grain distribution was inhomogeneous in the direction of the external field gradient. The nucleation gradually decreased in the direction of change.

Abstract: A series of shear thickening fluids (STF) were prepared and characterized by Rheometer. The stab resistance of Kevlar and ultrahigh molecular weight polyethylene (UHMWPE) non-woven fabrics impregnated with STF were investigated and found to exhibit significant improvements over neat fabric targets of equivalent weight. Specifically, dramatic improvements in stab resistance (knife threat) were observed. These novel materials could be potentially used to fabricate flexible body armors which provide improved protection against both stab and ballistic threats.

Abstract: The surface irradiation of 6063 aluminum alloy by high current pulsed electron was conducted with the aim of replacing the complicated pre-treatment in the processes of electroless plating. To explore the microstructure changes, optical metallography, SEM (scanning electron microscope), XRD (X-ray diffraction) analyses were carried out, and the sliding tests were used for the detection of wear resistance. It was concluded that the HCPEB irradiation could replace the pre-treatment of aluminum substrate as required in conventional electroless plating with a decreased surface roughness of Ni-P alloy plating layer. The plates exhibited an amorphous microstructure as demonstrated by XRD analysis. The plates, produced with the routine of HCPEB irradiation, activation and electroless plating possess, also exhibited good quality, even better than that of conventional electroless plating technique.

Abstract: Nanocrystalline aluminium bulk material with average grain size of 25.2 nm was prepared by warm-vacuum-compaction method. The as-prepared nanocrystalline aluminium was characterized by X-ray diffraction (XRD), differential scanning calarmeutry analysis (DSC), thermogravimetric analysis (TG), and Microhardness test, respectively. The experimental results show that the average grain size and microstrain of the nanocrystalline aluminium are 25.2 nm and 0.018%, respectively. The melting point of as-prepared nanocrystalline aluminium is 918.9 K, which is lower than that of coarse-grained aluminium by 14 K. The endothermic value of nanocrystalline aluminium is 196.3J/g. The average microhardness of the as-prepared nanocrystalline aluminium is 1.65 GPa, which is 11 times higher than that of coarse-grained aluminium.